Development of Flex Blogging system from zero based on FLEX4 technology: 7 Using JPA

APP engine Java supports not only JDO but also JPA in data storage. 4th, 5 lesson we are storing data using JDO, this lesson take a look if using JPA.

One, Using JPA

Open the Gapp_flexblog project, and in the src/meta-inf/directory, add the Persistence.xml file, which reads as follows:

<?xml　version="1.0"　encoding="UTF-8"　?>
<persistence　xmlns="http://java.sun.com/xml/ns/persistence"
　 　　xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
　 　　xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
　 　 　 　 http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"　version="1.0">
　 　　<persistence-unit　name="transactions-optional">
　 　 　 　　<provider>org.datanucleus.store.appengine.jpa.DatastorePersistenceProvider</provider>
　 　 　 　　<properties>
　 　 　 　 　 　　<property　name="datanucleus.NontransactionalRead"　value="true"/>
　 　 　 　 　 　　<property　name="datanucleus.NontransactionalWrite"　value="true"/>
　 　 　 　 　 　　<property　name="datanucleus.ConnectionURL"　value="appengine"/>
　 　 　 　　</properties>
　 　　</persistence-unit>
</persistence>

Where Persistence-unit's name is used when instantiating entitymanagerfactory.

In the Sban.flexblog.managers directory, add Class Emfactory:

package　sban.flexblog.managers;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

public　final　class　EMFactory　{
　 　 　 　　private　static　EntityManagerFactory _instance = Persistence
　 　 　 　 　 　 　 　 　 　 　 　 .createEntityManagerFactory("transactions-optional");

　 　 　 　　private　EMFactory()　{
　 　 　 　　}

　 　 　 　　public　static　EntityManagerFactory getInstance()　{
　 　 　 　 　 　 　 　　return　_instance;
　 　 　 　　}

}

This class is used to return an instance of entitymanagerfactory where the parameter "transactions-optional" is defined above.

Add entity class greetingentity to the Sban.flexblog directory:

Package sban.flexblog;
Import Java.util.Date;

Import javax.persistence.Entity;
Import Javax.persistence.GeneratedValue;
Import Javax.persistence.GenerationType;
Import Javax.persistence.Id;

@Entity
public class Greetingentity {

Public greetingentity (string user, string content, date date)
{
This.user = user;
This.greetingcontent=content;
This.date = date;
}

@Id
@GeneratedValue (strategy = generationtype.identity)
Private Long ID;

Private String user;

Private String greetingcontent;

private date date;

Public Long getId ()
{
return this.id;
}

Public String getgreetingcontent ()
{
return this.greetingcontent;
}

public void Setgreetingcontent (String v)
{
This.greetingcontent = v;
}

Public Date getDate ()
{
return this.date;
}
}